1. Field of the Invention
The present invention relates to an exposure apparatus for exposing a substrate using a plurality of stages under a projection optical system. More specifically, the present invention relates to an air conditioning of the exposure apparatus.
2. Description of the Related Art
A projection exposure apparatus for exposing a circuit pattern drawn on a reticle (mask) onto a substrate by means of a projection optical system has conventionally been used, and recently, there is an increasing demand for the exposure apparatus of higher resolution and more economical. Therefore, the exposure apparatus capable of performing an exposure process onto an increased number of substrates in a unit of time, namely, the exposure apparatus having better productivity is required. In order to respond to such a demand, a system for an exposure apparatus is discussed by Japanese Patent Application Laid-Open No. 2005-317916. That is, the exposure apparatus performs a conveyance operation for replacing a substrate by using another stage, and various measurement operations as to the substrate at the same time while the exposure apparatus is performing exposure of the substrate and adjusting a position with a stage under the projection optical system. After all operations end, the stage arranged under the projection optically system moves to a measurement operation region for performing a conveyance operation and a substrate measurement operation, and the stage arranged in the measurement operation region further moves to an exposure operation region for performing the exposure operation.
A position measurement of the stage in the exposure apparatus has been performed normally by using an interferometric length measuring device. The interferometric length measuring device is frequently used in a position measurement of a stage that requires a high-accuracy orientation control because the interferometric length measuring device has a high resolution function. On the other hand, the interferometric length measuring device tends to cause a measurement error due to an environmental change around a light path. Therefore, the more the high-accuracy measurement is required, the more the environmental change around the light path needs to be suppressed or the more a compensation technique is required. Examples of well-known factors of the measurement error due to the environmental change include a temperature change, a humidity change, and a pressure (barometric pressure and sound pressure) change. A change of ratio of components of air may cause the measurement error according to the circumstances. When an operator tries to measure a position of a stage by using the interferometric length measuring device within the exposure apparatus with a precision equal to or less than 1 nm, it is required to suppress the environmental change around the interferometer light path to a degree of a temperature of 1/1,000° C., a humidity of 0.1%, and a pressure of 1 Pa, or to perform a certain kind of real time compensation.
On the other hand, the stage within the exposure apparatus includes a heat source such as an exposure heat generated by an irradiation with exposure light, various actuators and sensors, and the like, and thus a temperature change of 0.01° C. level will occur on a stage surface even if cooling processing is performed on the stage surface. Therefore, in addition to a simple blowing of the high accuracy air conditioning to a region around the interferometer light path, various techniques have been discussed for the exposure apparatus so that an environmental change is suppressed as much as possible. For example, according to Japanese Patent Application Laid-Open Publication No. 05-126522, by changing a configuration of an air conditioning blow unit according to movement of the stage, the highly accurately temperature-controlled air conditioning is blown to only a vicinity of a measuring beam. Further, Japanese Patent Application Laid-Open Publication No. 2000-36453 discusses such a system that a flow balance of the supply opening is changed according to a position of the stage in order to give a constant temperature-regulated air flow to the stage disregarding the position of the stage.
However, in Japanese Patent Application Laid-Open Publication Nos. 05-126522 and 2000-36453, an air conditioning is performed based only on positional information of the stage, and it is difficult to achieve an efficient air conditioning by this method. This is because a disturbance of air conditioning depends to a large degree on a movement operation (hereinafter referred to as the “operation”), so that it is necessary to consider the movement of the stage in order to achieve the efficient air conditioning.
Generally, when a stage is moved in a larger stroke, the air conditioning around the interferometer light path tends to be disturbed, as compared to stage movement in a smaller stroke. For example, an exposure apparatus in which an exposure operation region and a measurement operation region are independently provided as discussed in Japanese Patent Application Laid-Open Publication No. 2005-317916, disturbance of the air conditioning due to the stroke of the stage movement appears more markedly.
Even if the stage is not moved in a large stroke, when a stage operation requiring a high accuracy positioning needs to be performed, it is necessary that the air conditioning around the interferometer light path is not disturbed as much as possible.
If the air conditioning is performed without taking into consideration a degree of disturbance of the air conditioning caused by the stage operation or the air conditioning accuracy required by the stage operation, a next task cannot be taken before the air conditioning comes to be desired one. Thus, throughput is decreased.